A lamp configured to be fixedly mounted on a wall, a roof or a cabinet or in other positions usually includes a mounting base and a lamp body, and the lamp body is fixedly connected to the mounting base by screws and other connecting pieces at the center or edge. The lamp body fixed at the center should be dismounted during mounting the lamp, so that the process is time-consuming and laborious. For the lamp body fixed at the edge, a connector will be clamped outside the lamp body, thereby affecting the overall aesthetics of the product. Moreover, no matter it is fixed at the center or at the edge, the mounting positions of the lamp body cannot be adjusted after being mounted, but only can be adjusted by dismounting the lamp body for re-mounting, thus resulting in inconvenience in mounting.